Make AppHarness dependencies installable

news/6974.bugfix.md

@@ -0,0 +1 @@
+Make `reflex.testing` importable without test-only dependencies and provide a `testing` extra for `AppHarness`.

pyproject.toml

@@ -66,6 +66,11 @@ db = [
   "sqlmodel >=0.0.24,<0.1",
 ]
 pydantic = ["reflex-base[pydantic]"]
+testing = [
+  "psutil >=7.0.0,<8.0",
+  "selenium >=4.0.0,<5.0",
+  "uvicorn >=0.34.0,<1.0",
+]
 
 [project.urls]
 homepage = "https://reflex.dev"

reflex/testing.py

@@ -25,7 +25,6 @@
 from pathlib import Path
 from typing import TYPE_CHECKING, Any, ClassVar, Literal, TypeVar
 
-import uvicorn
 from reflex_base.components.memo import MEMOS
 from reflex_base.config import get_config, reload_config
 from reflex_base.environment import environment
@@ -61,12 +60,34 @@
 except ImportError:
     has_selenium = False
 
+if TYPE_CHECKING:
+    import uvicorn
+
 # The timeout (minutes) to check for the port.
 DEFAULT_TIMEOUT = 15
 POLL_INTERVAL = 0.25
 FRONTEND_POPEN_ARGS = {}
 T = TypeVar("T")
 TimeoutType = int | float | None
+
+
+def _get_uvicorn():
+    """Import uvicorn for an AppHarness server.
+
+    Returns:
+        The imported uvicorn module.
+    """
+    try:
+        import uvicorn
+    except ImportError as exc:
+        msg = (
+            "AppHarness backend support requires `uvicorn`. Install it with "
+            "`pip install 'reflex[testing]'`."
+        )
+        raise ImportError(msg) from exc
+    return uvicorn
+
+
 if platform.system() == "Windows":
     FRONTEND_POPEN_ARGS["creationflags"] = subprocess.CREATE_NEW_PROCESS_GROUP  # pyright: ignore [reportAttributeAccessIssue]
     FRONTEND_POPEN_ARGS["shell"] = True
@@ -341,6 +362,7 @@ def _start_backend(self, port: int = 0):
         if self.app_asgi is None:
             msg = "App was not initialized."
             raise RuntimeError(msg)
+        uvicorn = _get_uvicorn()
         self.backend = uvicorn.Server(
             uvicorn.Config(
                 app=self.app_asgi,
@@ -470,7 +492,14 @@ def __enter__(self) -> Self:
 
     def stop(self) -> None:
         """Stop the frontend and backend servers."""
-        import psutil
+        try:
+            import psutil
+        except ImportError as exc:
+            msg = (
+                "AppHarness cleanup requires `psutil`. Install it with "
+                "`pip install 'reflex[testing]'`."
+            )
+            raise ImportError(msg) from exc
 
         # Quit browsers first to avoid any lingering events being sent during shutdown.
         for driver in self._frontends:
@@ -825,6 +854,7 @@ class AppHarnessProd(AppHarness):
     frontend_server: uvicorn.Server | None = None
 
     def _run_frontend(self):
+        uvicorn = _get_uvicorn()
         with chdir(self.app_path):
             frontend_app = reflex.utils.exec._frontend_prod_app()
         self.frontend_server = uvicorn.Server(
@@ -893,6 +923,7 @@ def _start_backend(self):
             msg = "App was not initialized."
             raise RuntimeError(msg)
         environment.REFLEX_SKIP_COMPILE.set(True)
+        uvicorn = _get_uvicorn()
         self.backend = uvicorn.Server(
             uvicorn.Config(
                 app=self.app_asgi,

tests/units/test_testing.py

@@ -19,6 +19,11 @@
 from reflex.utils.exec import should_prerender_routes
 
 
+def test_testing_module_does_not_import_uvicorn_at_module_load():
+    """Importing reflex.testing does not require the AppHarness backend runtime."""
+    assert "uvicorn" not in reflex_testing.__dict__
+
+
 @pytest.mark.skip("Slow test that makes network requests.")
 def test_app_harness(tmp_path):
     """Ensure that AppHarness can compile and start an app.